A basic wireless charging system may include a wireless power transmitter unit (PTU) and a wireless power receiving unit (PRU). For example, a PTU may include a transmit (Tx) coil and a PRU may include receive (Rx) coil. The Tx and Rx coils may be referred to as induction coils. In a typical induction charger, the Tx coil creates an alternating electromagnetic field and the Rx coil takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in proximity combine to form an electrical transformer. Greater distances between sender and receiver coils can be achieved when the inductive charging system uses resonant inductive coupling.
In some cases, a PRU may be implemented in a computing device, such as a mobile computing device, that can be placed on a charging mat including a PTU. The wireless energy emitted by the PTU is subject to various industry standards and regulatory standards that limit the level of power that RF transmitters are allowed to emit. For example, organizations such as Alliance for Wireless Power (A4WP), and Wireless Power Consortium (WPC) among others define standards for interoperability such as the frequency of operation and other parameters that define magnitude of fields and power levels in wireless power systems. Such systems should also conform to regulatory standards for RF exposure as required by regulatory bodies such as the US Federal Communications Commission (FCC) and guidelines by the International Commission on Non-Ionizing Radiation (ICNIRP)
The same numbers are used throughout the disclosure and the figures to reference like components and features. Numbers in the 100 series refer to features originally found in FIG. 1; numbers in the 200 series refer to features originally found in FIG. 2; and so on.